Legionella is a Gram negative bacterium, including many species that cause legionellosis or Legionaires' disease, most notably L. pneumophilia. They are a common species of bacteria that exist in many environments, with at least 48 species and 70 serogroups identified. On the side-chains of the cell wall are carried the bases for the somatic antigen specifity of these organisms. The chemical composition of these side chains both with respect to components as well as arrangement of the different sugars determines the nature of the somatic or O antigen determinants, which are such important means of serologically classifying many Gram-negative bacteria.
Legionella Human Infection
Legionella causes potentially fatal human infection Legionaires' disease and a lesser form of Pontiac fever. It is transmitted through inhaling mist droplets containing the bacteria. Common sources include cooling towers, domestic hot water systems, fountains, and similar diseminators that tap into a public water supply. Its natural environment include reservoirs of freshwater such as ponds and creeks.
Once inside a host, the bacteria may take up to 2 weeks to incubate before symptoms occur. Initial symptoms are flu-like, including fevers, chills, and dry coughs. Advanced stages of the disease causes problems with the gastro-intestinal tract and the nervous system and lead to diarrhea and nausea, respectively. Other advanced symptoms of pneumonia are also present.
However, the disease is generally not a threat to most healthy individuals, and only tend to lead to harmful symptoms in those with a compromised immune system, children, and the elderly. Due to this nature, it is actively checked for in the water systems of hospitals and nursing homes.
In the United States, the disease affects between 8,000 to 18,000 individuals a year.
The content of this page is retrieved from http://en.wikipedia.org/wiki/Legionella under GFDL
